David Element's Wildlife Web Page Butterflies 25

David Element

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____ Butterflies 25 - Nymphalidae - Commas 1

COMMA BUTTERFLY Polygonia c-album

COMMA BUTTERFLY LARVA Polygonia c-album

The upperside, underside and fully grown larva of this highly distinctive species are shown. The eponymous white markings are visible in the second photograph. In this case the generic and specific scientific names are both very appropriate. Two forms of the adult butterflies occur. Summer brood var. hutchinsoni butterflies (see Butterflies 7) are brighter than the typical form adults and they may be confused with Silver-washed Fritillaries (see Butterflies 5) which have a similar ground colour. These bright butterflies are produced in greater numbers during warm Spring weather and studies have shown that the larvae are capable of producing either typical (overwintering) or short-lived hutchinsoni adults depending upon the number of hours of daylight available. The hutchinsoni adults give rise to an additional generation of typical overwintering butterflies and help to consolidate the popoulation. This fast-track strategy therefore enables this species to take advantage of favourable conditions. A very good account of the life-history is given in the much sought after 'The Butterflies of Britain & Ireland', Jeremy Thomas and Richard Lewington, Dorling Kindersley, 1991. ISBN 0-86318-591-6, a superb reference work which is sadly no longer in print. Despite the significant decline of Elm, one of the principal larval foodplants, this butterfly remains common, in contrast to the well known and dramatic population crash which occurred during the nineteenth century. Other food sources are utilised including Hop and Stinging Nettle. The root cause of this crash has never been fully explained. Likely candidates include disease, parasitism or unfavourable climate change. There is an unfortunate parallel with the present fate of the Large Tortoiseshell, although this species has probably never been established as firmly in the UK and may be (?temporarily) losing the battle against parasitism.